Low vitamin D levels linked to metabolic syndrome

Increasing blood levels of vitamin D are linked to a lower prevalence of the metabolic syndrome, as well as improved ‘good’ cholesterol levels, says a new study.

According to findings published in the Journal of Clinical Lipidology​, the lowest levels of the sunshine vitamin were associated with a 31 per cent prevalence of metabolic syndrome, compared to only 10 per cent for people wit the highest average levels.

The researchers noted that the results do not prove that low vitamin D levels contributes or causes metabolic syndrome, and called for more studies to “assess whether increasing vitamin D intake will improve the metabolic cardiovascular risk factor profile”​.

“Although previous surveys have also reported associations between low 25(OH)D concentration and metabolic syndrome components, to our knowledge, the present investigation is the first to report this finding in a sample with a high prevalence of vitamin D dietary supplement users in which frequencies of vitamin D insufficiency and deficiency were low,”​ wrote the researchers, led by Kevin Maki from Illinois-based Provident Clinical Research

Metabolic syndrome (MetS) is a condition characterised by central obesity, hypertension, and disturbed glucose and insulin metabolism. The syndrome has been linked to increased risks of both type-2 diabetes and cardiovascular disease (CVD).

Study details​

The researchers analysed vitamin D levels in the blood of 257 men and women aged over 18. Dietary and supplementary intakes were assessed using a food frequency and dietary supplement questionnaires, said the researchers.

“The most notable finding from the present study was the strong relationship between serum concentrations of 25(OH)D and HDL-C concentrations,”​ wrote the researchers.

“Each 10 ng/mL increment in 25(OH)D was associated with an increase of 3.8 to 4.2 mg/dL in HDL-C [...] This is of considerable potential importance given that each 1 mg/dL increment in HDL-C is associated with a 4 to 6 per cent reduction in coronary heart disease (CHD) risk.”​

They also observed inverse associations between vitamin D levels and triglyceride levels, body mass index, and waist circumference, meaning that higher vitamin D levels were associated with lower values for these measurables.

Explanation​

“A potential explanation for our observation of an inverse association between 25(OH)D and indicators of adiposity (waist and body mass index) may be that vitamin D is fat soluble and is therefore easily sequestered in adipose tissue,”​ wrote the researchers.

“Thus, there is a greater storage capacity for vitamin D in overweight and obese individuals, which may result in a reduced circulating concentration of 25(OH)D. ​

“As a result, in order to maintain a given circulating 25(OH)D concentration, overweight and obese individuals may have to consume higher quantities of vitamin D than would be the case for normal weight populations,”​ they said.